Switch



B. DICK SWITCH March 10, .1942.

Filed 001;. 11, 1939 mm o m. 0m 4/ mm mm v m N hm mm 7 5i INVEN TOR BURNS DICK ATTORNEY Patented Mar. 10, 1942 swrron Burns Dick, Ferguson, Mo., assignor to Wagner Electric Corporation, St. Louis, Mo., a corporation of Delaware Application October 11, 1939, Serial No. 298,899

' 4 Claims. (or. zoom-s9) My invention relates to electrical switches and more particularly to a switch for operating a signal such as the stop light on a motor vehicle.

One of the objects of my invention is to pro vide an improved electrical switch construction which can be associated with a push-rod .em-.

ployed in applying a force to a displaceable member.

Another and more specific object of my invention is to so construct a switch and associate it with a piston rod of a master cylinder device for fluid-actuated brakes that the switch will be normally open when the brakes are inoperative and closedwhen the brake pedal is initially operated and prior to applying pressure to the brakes, said switch also being so associated with the rod that it will not act as a force transmitting means when the piston is displaced.

Another object of my invention is to so embody a signal control switch in the piston rod of a master cylinder device that it will become closed to operate the signal when the master cylinder is inoperative and the parts thereof are not correctly adjusted, thus indicating to the operator that certain adjustments are necessary.

Other objects of my invention will become apparent from. the following description taken in connection with the accompanying drawing in is a face view of thespring plate contacting ele-- ment of the switch.

Referring to the drawing in detail, I indicates a well-known type of master cylinder having a cylinder 2 connected to the fluid motors 3 of brakes t and a piston 5 for applying pressure to the fluid. The head 6 of the piston has associated therewith a packing cup I and the piston is normally biased to its inoperative position by a spring 8 interposed between the cup and the end of the cylinder. The retracted or inoperative position of the piston is determined by the stop 9 and when the piston is in this position, the cup uncovers the porthole l0 and places the cylinder ahead of the piston in communication with the reservoir H to allow for expansion and contraction of the fluid in the system, and also to supply any lost fluid or to permit excessfluid to return to the reservoir. The rear of the piston is provided with a packing cup I! to form a sealed chamber around the piston, which chamber is connected to the reservoir by a passage 13. The head of the cup is provided with passages lfl permitting fluid to flow past the cup during its retractile stroke and thus prevent subatmospheric pressure from existing in the system in the event the piston is retracted faster than the fluid is returned from the fluid motors ,3.

The push-rod for the piston comprises two rods 1 5 and IS, the former telescoping in the latter which cooperates with a socket in the piston. The outer end of rod it of the push-rod carries an adjustable clevis I1 and is pivotally 3 connected to a brake pedal l8 biased to an inoperative position against a stop I9 by a spring 20. The rod l5 has a shoulder 2i for abutment against the end of rod I6 whereby force can be transmitted from the pedal to the piston. A spring 22, weaker than spring 8, is interposed between the telescoping ends of rods l5 and 16 to bias the shoulder 2| away from the end of rod It. A screw stop 23 cooperating with a shoulder 24 carried by the inner end of rod l5 determines the extent of lost the rods.

A member 25 of insulating material is threaded on the end of rod I6 and carried by this member are two electrical contacts 26 and 21 extending fromconnecting sockets 28 and 29, respectively. A second member til of insulating material is'clamped on rod it by a nut 3| and carried by the peripheral portion of this member is a dished metal spring plate 32 for cooper- .ating with the contacts 26 and 2'! to electrically connect them together under certain conditions. The contact 26 is connected to a grounded, battery 33 by a conductor 34 and the contact 21 is connected to a grounded stop light r other signal device 35 by a conductor 36, thus completing the electrical circuit. In order that the switch structure may be protected from dust and dirt, the outer end of the dust excluding boot 3! of the master cylinder is extended to enclose both members 25 and 30.

When the master cylinder device is inpperative and the brakes released, the parts are in the positions shown in Figure 1. The clevis H is so adjusted that with the pedal against the stop i9 and the piston in retracted position against stop 9, the shoulder 2| will be held away from the end of rod it by the light spring 22. The

rod l6 will be in engagement with th piston.

motion between,

and as the pedal continues to be moved, force will be transmitted to the piston and. cause it to apply pressure to the fluid ond actuate the bruises. The switch will remain closed until. the brakes are Irelcosed end the ports weturn to then i'espective positions shown in Fi ure 1.

The switch construction and the manner in which it is essocloted with the master cylinder and the pushorod also permits the signed system to not as o worming in the event certoin odjust merits use not cot-sect. The pedal stop to is generally Cfii'iltld on the body of the vehicle and may even be the i-loorboercl whereas the master cylindei" and pedal are mounted on the chassis. llt is thus possible that the stop may assume such o. position that the pedol cannot return to its proper oi? position and permit the piston to assume its normal inoperative position o. few thousondths of on inch book of the porthole iii. If the porthole is not uncovered, the brakes may not be fully released Oi? if released, they may be caused to be re-upplied sufficiently to drag in the event of an increase in temperature causing expansion of the fluid. If this occurs, the switch will be held closed and the operator will know that ii the stop light remains lighted after the pedal is released, then the braking system needs attention and adjustment.

It is to be noted that the switch and push-rod construction may be made economically and readily substituted for existing push-rods. Also, there is no danger of the switch afiectlng the fluid braking system as would be the case where the switch is closely associated with the fluid system and operated by fluid pressure therein. In the latter type of switch, a short circuit may cause sulllcient heat to gas the fluid and cause loss of brakes or even such damage that some of the fluid will escape.

, Being aware of the possibility of modifications in the particular structure herein described without departing from the fundamental principles of my invention, I do not intend that its scope be limited except as set forth by the appended claims.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In braking apparatus, a master cylinder for producing fluid pressure, a. member for operating said device, a push-rod between the memher and master cylinder and comprising two parts capable of relative movement prior to operating the master cylinder, .a normally open electrical switch so mounted and associated with position it the stop tor the not cayenne the parts as to be caused to assume closed posttion by the relativemovement or the parts to" ward each other, and a dust excluding boot our-- rounding the push-rod and enclosing the switch.

2. In a fluid pressure braking system, a master cylinder device having a movable piston, a tetractile stop for the piston, on octuoting membet, a connection between the membei: and pieton, o retractile stop for the actuating member, and switch means so associated with the con nection that said switch moons gaging its i'etroctile stop.

3. in o fluid pressure broking tet cylinder device comprising: e. l

reservoii', o. poithole betw cylinder and o. stop for t i so positioned us to perm uncovered by the pistoi gages the stop, an actuotii its stop and the stop ioi the octui lug is properly positioned relative to the pistol; stop, and e. switch so associated with said connecting elements that it will be open whet-o the actuating member is retracted and the stops ore properly positioned, the switch if open under combtions and fluid pressure is present in the master cylinder device then said open switch will be on indication that said fluid pressure is caused by the improper position of the piston stop oreventing the piston from uncovering. the porthole and not the improper relative position of the stops.

4. In braking apparatus, a force transmitting connection between an actuated element and an actuating element and comprising two rods provided with abutments whereby when they are engaged force can be transmitted by the rods, means biasing the two rods to normally lnoperative positions permitting relative movement prior to engagement'of the abutments, a member of insulating material secured to each rod, said members being axially spaced apart, two diametrically positioned electrical contacts carried by one member and projecting toward the other member, a disk-like element or conducting ma.- terial carried by the other member and axially spaced from the contacts when the rods are in their normally inoperative positions mt capable of engaging the contacts when the rods are moved relatively and prior to engagement of the abutments, said disk-like member being so constructed and mounted as to be axially yieldable to permit engagement of the abutments after it engages the contacts.

BURNS DICK. 

